1. Field of the Invention
The present invention relates to a crystalline silica and especially to a crystalline silica which is catalytically active and selective in methylation reactions.
2. The Prior Art
A process for selectively producing para-xylene is disclosed in U.S. Pat. No. 4,270,017. Para-xylene is selectively prepared by reacting toluene and a methylating agent in the presence of a phosphorus modified catalyst comprising a silica polymorph intermixed with an inorganic refractory oxide.
U.S. Pat. Nos. 4,325,929 and 4,344,927 relate to a process for hydrothermally preparing a silica polymorph which is described as suitable for use in aromatic alkylation.
U.S. Pat. No. 4,362,653 discloses a catalyst composite comprising a silica polymorph and the use of the catalyst in a hydrocarbon reforming process.
Crystalline silicas and their use as alkylation catalysts are disclosed in U.S. Pat. No. 4,283,306. The patent additionally teaches the use of various promoters combined with the catalysts.
Hydrogenation catalysts are disclosed in U.S. Pat. No. 4,387,258 which relates to palladium or platinum promoters deposited on a low acidity silica polymorph/silicalite/high sillica zeolite.
It is an object of the present invention to provide a crystalline silica for use in catalytically promoting the conversion of hydrocarbons.
Another object of the invention is to provide a catalytically active crystalline silica that is selective for the production of para-xylene.
Yet another object of the invention is to provide a process for the production of para-xylene using catalysts containing said crystalline silica.
Still another object of the invention is to provide a process for producing a crystalline silica.
Other objects and advantages of the invention will be apparent from the following description.